Python: Image is not moving

Question

I want to move an image in python/pygame, but it doesn't work, python doesn't even notice that the key is pressed. I found solutions and compared my code to others, but it still doesn't work... I'm very new to coding (started only this week) please correct my code

import pygame

pygame.init()

display_width = 800
display_height = 600

black = (0,0,0)
white = (255,255,255)
bright_red = (255,0,0)
bright_green = (0,255,0)
red = (200,0,0)
green = (0,200,0)

gameDisplay = pygame.display.set_mode((display_width,display_height))

smileImg = pygame.image.load('mouth.png')
clock = pygame.time.Clock()

def smile(x,y):
    gameDisplay.blit(smileImg, (x,y))





x = (display_width * 0.45)
y = (display_height * 0.8) 
go = 0

gameExit = False
while not gameExit:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            quit()

        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_BACKSPACE:
                go = -10


        if event.type == pygame.KEYUP:
            if event.key == pygame.K_BACKSPACE:
                go = 0
    y += go
    gameDisplay.fill(white)
    smile(x,y)
    pygame.display.update()
    clock.tick(60)


pygame.quit()
quit()